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Short Exposure (short + exposure)
Selected AbstractsShort exposure to high levels of fluoride induces stage-dependent structural changes in ameloblasts and enamel mineralizationEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 2006D. M. Lyaruu We tested the hypothesis that the sensitivity of forming dental enamel to fluoride (F,) is ameloblast developmental stage-dependent and that enamel mineralization disturbances at the surface of fluorotic enamel are caused by damage to late-secretory- and transitional-stage ameloblasts. Four-day-old hamsters received a single intraperitoneal dose of 2.5,20 mg NaF/kg body weight and were examined, 24 h later, by histology and histochemistry. A single dose of ,,5 mg of NaF/kg induced the formation of a hyper- followed by a hypomineralized band in the secretory enamel, without changing the ameloblast structure. At 10 mg of NaF/kg, cystic lesions became apparent under isolated populations of distorted late-secretory- and transitional-stage ameloblasts. Staining with von Kossa stain showed that the enamel under these lesions was hypermineralized. At 20 mg of NaF/kg, cystic lesions containing necrotic cells were also found in the early stages of secretory amelogenesis and were also accompanied with hypermineralization of the enamel surface. We concluded that the sensitivity to F, is ameloblast developmental stage-dependent. Groups of transitional ameloblasts are most sensitive, followed by those at early secretory stages. These data suggest that a F-induced increase in cell death in the transitional-stage ameloblasts accompanies the formation of cystic lesions, which may explain the formation of enamel pits seen clinically in erupted teeth. [source] Effects of meiosis-inhibiting agents and equine chorionic gonadotropin on nuclear maturation of canine oocytesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2003N. Songsasen Abstract Experiments were conducted to determine the effects of meiosis-inhibiting-agents and gonadotropins on nuclear maturation of canine oocytes. The culture medium was TCM199,+,10 ng/ml epidermal growth factor supplemented with 25 ,M ,-mercaptoethanol, 0.25 mM pyruvate, and 1.0 mM L-glutamine (Basal TCM). Initially, oocytes were cultured in Basal TCM alone or in Basal TCM,+,dibutylryl cyclic adenosine monophosphate (0.5, 1, 5, or 10 mM dbcAMP) for 24 hr. Dibutylryl cAMP inhibited resumption of meiosis in a dose-dependent manner; 60% of oocytes remained at the germinal vesicle (GV) stage after being cultured for 24 hr in 5 mM dbcAMP. The meiosis-inhibitory effect of dbcAMP appeared to be reversible, as the oocytes resumed meiosis and completed nuclear maturation after being cultured for an additional 48 hr in its absence. Oocytes were then cultured in Basal TCM alone or in Basal TCM,+,roscovitine (12.5, 25, or 50 ,M) for 24 hr. Although ,60% of oocytes cultured in 25 ,M roscovitine remained at the GV stage, this percentage was not significantly different from the 48% that also remained at the GV stage when cultured in its absence. Oocytes were cultured in Basal TCM,+ 25 ,M roscovitine for 17 hr, exposed briefly to equine chorionic gonadotropin (eCG), and then cultured in Basal TCM for 48 hr. Short exposure of oocytes to eCG was beneficial, as it significantly increased the proportion of oocytes developing beyond germinal vesicle breakdown (P,<,0.05) with ,20,30% of these were metaphase I (MI) oocytes. Study of the kinetics of nuclear maturation demonstrated that large numbers of oocytes remained at MI even after being cultured for 52 hr following brief exposure to eCG. This study showed that in vitro maturation of canine oocytes can be somewhat improved by short exposure of oocytes to eCG. However, further studies are still required to derive effective methods to mature canine oocytes in vitro. Mol. Reprod. Dev. 65: 435,445, 2003. © 2003 Wiley-Liss, Inc. [source] Reproductive function in male rats after brief in utero exposure to diethylstilboestrolINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 6 2000G. H. G. Behrens Long-term effects of brief in utero exposure to diethylstilboestrol (DES) during a foetal period known to be critical for gonadal development were evaluated. Rats were exposed to DES (100 ,g/kg body-weight) from day 17 to 19 of pregnancy. All of the DES-treated pregnant rats (11/11) ate parts or whole of their offspring during the first day after birth (p=0.03). Surviving male offspring were examined on day 63 post-partum. DES induced a reduction in weight of the testis (p=0.06) and ventral prostate (p=0.07), even after this short exposure. DES tended to reduce the number of Sertoli cells (p=0.13). Our findings indicate that even a short in utero exposure of rats to DES during a critical period for gonadal development results in cannibalism and reduced testis and ventral prostate weight. [source] Hypoxia increases normal prostate epithelial cell resistance to receptor-mediated apoptosis via AKT activationINTERNATIONAL JOURNAL OF CANCER, Issue 8 2009Sinead Walsh Abstract The aging prostate is associated with changes in its vascular structure, which could lead to changes in oxygen levels. Hypoxia is an important environmental change that leads to the progression of many cancers mediated through a number of cellular changes, which included resistance to apoptosis. The role of hypoxia in initiating tumour development has not been previously investigated. We demonstrate that normal prostate epithelial cells develop a resistance to receptor-mediated apoptosis following 24 hr of 1% hypoxia. This effect is associated with the altered expression of a number of pro- and anti-apoptotic proteins, which leads to inhibition of Cytochrome c release and downstream caspase activation. This is mediated via decreased Bax translocation and upstream Caspase 8 activity. Despite increased expression of cIAP-2, small interfering RNA (siRNA) knockdown does not restore susceptibility to TRAIL-induced apoptosis. Gene expression analysis indicated potential changes in AKT activation, which was confirmed by increased phosphorylation of AKT. Inhibition of this phosphorylation reversed the resistance to TRAIL-induced apoptosis. AKT activation is emerging as a key survival signal in prostate cancer. This study demonstrates that short exposure to low oxygen can increase resistance to immune surveillance mechanisms and might confer a survival advantage onto normal prostate epithelial cells so that they can survive subsequent genomic instability and other carcinogenetic insults leading to the early development of prostate cancer. © 2008 Wiley-Liss, Inc. [source] Non-apoptogenic killing of hela cervical carcinoma cells after short exposure to the alkylating agent N -methyl- N, -nitro- N -nitrosoguanidine (MNNG)JOURNAL OF CELLULAR BIOCHEMISTRY, Issue 6 2003Józefa W, sierska-G Abstract We examined the action of N -methyl- N, -nitro- N -nitrosoguanidine (MNNG) on HeLa cells and compared it with that of cisplatin (CP). MNNG directly killed a substantial number of cells within 1 hour and resulted in strong DNA-damage as evidenced by Comet measurements. Despite appearance of DNA lesions, p53 protein was not activated. Analysis of HeLa cells treated with MNNG for 1h, 3h and 6h by flow cytometry and by Hoechst staining did not reveal any sub-G1 cell population and chromatin condensation/fragmentation characteristic for apoptosis, respectively. Also, no biochemical changes typical for apoptosis such as activation of caspase-3 or release of cytochrome C from mitochondria were detected. Inactivation of PARP-1 reduced the direct cytotoxicity exerted by MNNG. Our results showing that despite appearance of severe DNA lesions after short exposure of HeLa cells to MNNG neither activation of p53 response nor induction of apoptosis occurred implicate that generation of strong DNA damage is not sufficient to stabilize p53 protein in HeLa cells. Our data unequivocally show that the conscientious determination of the type of cell death induced by genotoxic agents is necessary. The assessment of the changes based on at least a few independent criteria is required to discriminate between apoptosis and necrosis. Since the alkylating agents generate DNA strand breaks, the recruitment of methods based on determination of DNA cleavage such as DNA ladder or TUNEL assay for evaluation of apoptosis is not adequate. © 2003 Wiley-Liss, Inc. [source] Inhalation efficacy of RFI-641 in an African green monkey model of RSV infectionJOURNAL OF MEDICAL PRIMATOLOGY, Issue 2 2003W.J. Weiss Abstract: Human respiratory syncytial virus (RSV) is a major cause of acute upper and lower respiratory tract infections. RFI-641 is a novel RSV fusion inhibitor with potent in vitro activity. In vivo efficacy of RFI was determined in an African green monkey model of RSV infection involving prophylactic and therapeutic administration by inhalation exposure. Inhalation was with an RFI-641 nebulizer reservoir concentration of 15 mg/ml for 15 minutes (short exposure) or 2 hours (long exposure). Efficacy and RFI-641 exposure was determined by collection of throat swabs, nasal washes and bronchial alveolar lavage (BAL) on selected days. The short-exposure group (15 minutes) exhibited no effect on the nasal, throat or BAL samples. The throat and nasal samples for the long-exposure group failed to show a consistent reduction in viral titers. RFI-641 2 hours exposure-treated monkeys showed a statistically significantly log reduction for BAL samples of 0.73,1.34 PFU/ml (P -value 0.003) over all the sampling days. Analysis indicates that the long-exposure group titer was lower than the control titer on day 7 and when averaged across days. The results of this study demonstrate the ability of RFI-641 to reduce the viral load of RSV after inhalation exposure in the primate model of respiratory infection. [source] Differential Changes in MAP Kinases, Histone Modifications, and Liver Injury in Rats Acutely Treated With EthanolALCOHOLISM, Issue 9 2010Annayya R. Aroor Background:, Acute ethanol is known to affect cells and organs but the underlying molecular mechanisms are poorly explored. Recent developments highlight the potential importance of mitogen-activated protein kinases, MAPKs (i.e., ERK1/2, p38, and JNK1/2) signaling, and histone modifications (i.e., acetylation, methylation, and phosphorylation) in the actions of ethanol in hepatocytes. We have therefore investigated significance of these molecular steps in vivo using a model in which rats were acutely administered ethanol intraperitoneally (IP). Methods:, Ethanol was administered IP (3.5 gm/kg body weight) to 12-week-old male Sprague,Dawley rats. Liver was subsequently removed at 1 and 4 hours. Serum was used for alcohol and ALT assays. At the time of the removal of liver, small portions of each liver were formalin-fixed and stained with hematoxylin and eosin (H&E) and used for light microscopy. Western blot analysis was carried out with specific primary antibodies for various parameters. Results:, There were clear differences at 1 and 4 hours in blood ethanol, ALT, steatosis, and cleaved caspase 3. Apoptosis at 1 hour was followed by necrosis at 4 hours. Acute alcohol elicited a marked increase in the phosphorylation of ERK1/2 and moderate increases in the phosphorylation of p38 MAPK and JNK. Temporally different phosphorylation of histone H3 at ser-10 and ser-28 occurred and acetylation of histone H3 at lys 9 increased progressively. Conclusions:, There were distinct differences in the behavior of the activation of the 3 MAP kinases and histone modifications after acute short exposure of liver to ethanol in vivo. Although all 3 MAPKs were rapidly activated at 1 hour, the necrosis, occurring at 4 hours, correlated to sustained activation of ERK1/2. Transient activation of p38 is associated with rapid phosphorylation of histone H3, whereas prolonged activation of ERK1/2 is correlated to persistent histone H3 acetylation. [source] Effects of meiosis-inhibiting agents and equine chorionic gonadotropin on nuclear maturation of canine oocytesMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 4 2003N. Songsasen Abstract Experiments were conducted to determine the effects of meiosis-inhibiting-agents and gonadotropins on nuclear maturation of canine oocytes. The culture medium was TCM199,+,10 ng/ml epidermal growth factor supplemented with 25 ,M ,-mercaptoethanol, 0.25 mM pyruvate, and 1.0 mM L-glutamine (Basal TCM). Initially, oocytes were cultured in Basal TCM alone or in Basal TCM,+,dibutylryl cyclic adenosine monophosphate (0.5, 1, 5, or 10 mM dbcAMP) for 24 hr. Dibutylryl cAMP inhibited resumption of meiosis in a dose-dependent manner; 60% of oocytes remained at the germinal vesicle (GV) stage after being cultured for 24 hr in 5 mM dbcAMP. The meiosis-inhibitory effect of dbcAMP appeared to be reversible, as the oocytes resumed meiosis and completed nuclear maturation after being cultured for an additional 48 hr in its absence. Oocytes were then cultured in Basal TCM alone or in Basal TCM,+,roscovitine (12.5, 25, or 50 ,M) for 24 hr. Although ,60% of oocytes cultured in 25 ,M roscovitine remained at the GV stage, this percentage was not significantly different from the 48% that also remained at the GV stage when cultured in its absence. Oocytes were cultured in Basal TCM,+ 25 ,M roscovitine for 17 hr, exposed briefly to equine chorionic gonadotropin (eCG), and then cultured in Basal TCM for 48 hr. Short exposure of oocytes to eCG was beneficial, as it significantly increased the proportion of oocytes developing beyond germinal vesicle breakdown (P,<,0.05) with ,20,30% of these were metaphase I (MI) oocytes. Study of the kinetics of nuclear maturation demonstrated that large numbers of oocytes remained at MI even after being cultured for 52 hr following brief exposure to eCG. This study showed that in vitro maturation of canine oocytes can be somewhat improved by short exposure of oocytes to eCG. However, further studies are still required to derive effective methods to mature canine oocytes in vitro. Mol. Reprod. Dev. 65: 435,445, 2003. © 2003 Wiley-Liss, Inc. [source] Effects of fluorides on Candida albicansORAL DISEASES, Issue 4 2008S Flisfisch Aims:, To assess whether a short exposure of Candida albicans to commonly used fluorides would affect growth, cell surface hydrophobicity, and adherence to buccal epithelial cells. Methods:,Candida albicans ATCC 90028 and 11 clinical isolates were used. Minimal inhibitory concentrations (MICs) of sodium fluoride (NaF) and of an amine fluoride,/,stannous fluoride combination (AmF,/,SnF2) were determined. Yeasts were exposed to MICs of tested agents for 1 h. Subsequently, their growth was recorded spectrophotometrically. Their cell surface hydrophobicity was assessed with n -hexadecane. Adherence to buccal epithelial cells was determined microscopically. Phosphate buffered saline (PBS) and chlorhexidine digluconate (CHX) served as controls. All results were analyzed by one-way ANOVA. Results:, MICs of AmF,/,SnF2 and CHX varied between 1 and 4 ,g ml,1, whereas those of NaF were 15 000 ,g ml,1. Statistically significant growth inhibition was detected after AmF,/,SnF2 (OD24 h ± SD 0.457 ± 0.059) and CHX (0.175 ± 0.065) in comparison with PBS (0.925 ± 0.087) and NaF (0.813 ± 0.081). All strains demonstrated uniform behavior. Only minor changes in cell surface hydrophobicity and adherence to buccal epithelial cells (BEC) were detected. Conclusion:, Growth inhibition of AmF,/,SnF2 was comparable with that of CHX whereas NaF had a weaker effect. Exposure to the fluorides did not seem to alter the cell surface hydrophobicity nor adherence to BEC. [source] Influence of a short exposure to teflubenzuron residues on the predation of thrips by Iphiseius degenerans (Acari: Phytoseiidae) and Orius laevigatus (Hemiptera: Anthocoridae)PEST MANAGEMENT SCIENCE (FORMERLY: PESTICIDE SCIENCE), Issue 11 2003Alison S Scott Brown Abstract A short duration (24 h) leaf-disc bioassay was used to determine the effects of teflubenzuron residues on the predation levels of two predators, Iphiseius degenerans (Berlese) and Orius laevigatus (Fieber), foraging on nymphs of two species of thrips, Frankliniella occidentalis (Pergande) and Heliothrips haemorrhoidalis (Bouché), on a range of different species of plant. Teflubenzuron did cause thrips mortality during the 24-h bioassay; it was more active against H haemorrhoidalis than F occidentalis. Teflubenzuron did not cause significant mortality to either species of predator, although on some plants the effectiveness of both predators was reduced in the presence of teflubenzuron. Copyright © 2003 Society of Chemical Industry [source] Sub-optimal morning temperature induces photoinhibition in dense outdoor cultures of the alga Monodus subterraneus (Eustigmatophyta)PLANT CELL & ENVIRONMENT, Issue 10 2001A. Vonshak Abstract Diel changes in photosynthetic oxygen evolution and several photochemical parameters measured by chlorophyll fluorescence quenching and induction were measured in outdoor dense cultures of the alga Monodus subterraneus (Eustigmatophyta). Cultures were maintained under two temperature regimes. In one, a rise in temperature was initiated in the morning by the increase in solar radiation up to the optimal temperature of 28 °C; in the other, a heating device was used to increase the rate of warming up in early morning. Although the two cultures were maintained at the same temperature and light intensity for most of the day, cultures exposed for only a short time to suboptimal morning temperature showed a larger decrease in almost all the photosynthetic parameters. By comparing the diel changes in maximal photochemistry efficiency of photosystem II, the electron transport rate and the photochemical and non-photochemical chlorophyll fluorescence quenching of the cultures, we concluded that even a relatively short exposure to suboptimal morning temperatures induced photoinhibitory damage. The higher photochemical activity of the heated culture was also reflected in a significant increase in productivity, which was 60% higher in the morning heated cultures than in the non-heated cultures. [source] Occupational tuberculosis following extremely short exposureTHE CLINICAL RESPIRATORY JOURNAL, Issue 1 2009Zaza Kamper-Jűrgensen Abstract Introduction:, Transmission of Mycobacterium tuberculosis (MT) in most cases requires extended exposure. Objectives:, To document that MT transmission may occur even after very short exposure. Material and Methods:, All first-time culture-confirmed tuberculosis (TB) cases in Denmark have since 1992 been subjected to genotyping, using the IS6110 -Restriction Fragment Length Polymorphism (RFLP) technique. A young nurse with no risk factors developed pulmonary TB: the DNA pattern of her MT strain was compared to The Danish TB Subtyping Database, comprising >6000 DNA patterns from TB patients nationwide. Results:, Only one single MT DNA pattern matched the DNA profile of the isolate from the nurse. The pattern originated from a patient shortly admitted to the department where she worked at the time. MT transmission had occurred in spite of very short exposure. Conclusion:, By adding modern molecular epidemiological methods to traditional epidemiological surveys, a more detailed picture of MT-transmission pathways can be obtained, showing that MT transmission can occur even after extremely short exposure. This stresses the necessity for adequate respiratory protection among hospital staff taking care of patients with pulmonary symptoms suspected for TB. Please cite this paper as: Kamper-Jűrgensen Z, Lillebaek T and Andersen ĆB. Occupational tuberculosis following extremely short exposure. The Clinical Respiratory Journal 2009; 3: 55,57. [source] No effects of mobile phone use on cortical auditory change-detection in children: An ERP studyBIOELECTROMAGNETICS, Issue 3 2010Myoung Soo Kwon Abstract We investigated the effect of mobile phone use on the auditory sensory memory in children. Auditory event-related potentials (ERPs), P1, N2, mismatch negativity (MMN), and P3a, were recorded from 17 children, aged 11,12 years, in the recently developed multi-feature paradigm. This paradigm allows one to determine the neural change-detection profile consisting of several different types of acoustic changes. During the recording, an ordinary GSM (Global System for Mobile Communications) mobile phone emitting 902,MHz (pulsed at 217,Hz) electromagnetic field (EMF) was placed on the ear, over the left or right temporal area (SAR1g,=,1.14,W/kg, SAR10g,=,0.82,W/kg, peak value,=,1.21,W/kg). The EMF was either on or off in a single-blind manner. We found that a short exposure (two 6,min blocks for each side) to mobile phone EMF has no statistically significant effects on the neural change-detection profile measured with the MMN. Furthermore, the multi-feature paradigm was shown to be well suited for studies of perception accuracy and sensory memory in children. However, it should be noted that the present study only had sufficient statistical power to detect a large effect size. Bioelectromagnetics 31:191,199, 2010. © 2009 Wiley-Liss, Inc. [source] A novel purification strategy for retrovirus gene therapy vectors using heparin affinity chromatographyBIOTECHNOLOGY & BIOENGINEERING, Issue 4 2005María de las Mercedes Segura Abstract Membrane separation and chromatographic technologies are regarded as an attractive alternative to conventional academic small-scale ultracentrifugation procedures used for retrovirus purification. However, despite the increasing demands for purified retroviral vector preparations, new chromatography adsorbents with high specificity for the virus have not been reported. Heparin affinity chromatography is presented here as a novel convenient tool for retrovirus purification. The ability of bioactive retroviral particles to specifically bind to heparin ligands immobilized on a chromatographic gel is shown. A purification factor of 63 with a recovery of 61% of functional retroparticles was achieved using this single step. Tentacle heparin affinity supports captured retroviral particles more efficiently than conventional heparin affinity chromatography supports with which a lower recovery was obtained (18%). Intact, infective retroviral particles were recovered by elution with low salt concentrations (350 mM NaCl). Mild conditions for retrovirus elution from chromatographic columns are required to preserve virus infectivity. VSV-G pseudotyped retroviruses have shown to be very sensitive to high ionic strength, losing 50% of their activity and showing membrane damage after a short exposure to 1M NaCl. We also report a complete scaleable downstream processing scheme for the purification of MoMLV-derived vectors that involves sequential microfiltration and ultra/diafiltration steps for virus clarification and concentration respectively, followed by fractionation by heparin affinity chromatography and final polishing by size-exclusion chromatography. Overall, by using this strategy, a 38% yield of infective particles can be achieved with a final purification factor of 2,000. © 2005 Wiley Periodicals, Inc. [source] Conditioning attentional skills: examining the effects of the pace of television editing on children's attentionACTA PAEDIATRICA, Issue 10 2009NR Cooper Abstract Aim:, There is increasing concern about the behavioural and cognitive effects of watching television in childhood. Numerous studies have examined the effects of the amount of viewing time; however, to our knowledge, only one study has investigated whether the speed of editing of a programme may have an effect on behaviour. The purpose of the present study was to examine this question using a novel experimental paradigm. Methods:, School children (aged 4,7 years) were randomly assigned to one of two groups. Each group was presented with either a fast- or slow-edit 3.5-min film of a narrator reading a children's story. Immediately following film presentation, both groups were presented with a continuous test of attention. Results:, Performance varied according to experimental group and age. In particular, we found that children's orienting networks and error rates can be affected by a very short exposure to television. Conclusion:, Just 3.5 min of watching television can have a differential effect on the viewer depending on the pacing of the film editing. These findings highlight the potential of experimentally manipulating television exposure in children and emphasize the need for more research in this previously under-explored topic. [source] Oxidative stress biomarkers in bivalves transplanted to the Guadalquivir estuary after Aznalcóllar spillENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 1 2003Antonio Romero-Ruiz Abstract Biological effects of metals were studied in clams (Scrobicularia plana) transplanted to Guadalquivir estuary (Spain) at several times after the spill of toxic metals from Aznalcóllar pyrite mine (southwest Spain) (April 1998) using biochemical biomarkers responsive to reactive oxygen species. Significant As, Cd, Fe, Mn, Ni, and Pb uptake was found in clams living for seven months at the estuary (from July 1999). Increased activity of antioxidant (catalase, glucose-6-phosphate, and 6-phosphogluconate dehydrogenase) and glutathione-related (glutathione reductase and glyoxalase I and II) enzymes was also found after short exposures; the levels of malondialdehyde and metallothionein increased also, particularly with long exposures. Clams living four weeks at the estuary (from March 2000) but not at a reference site also accumulated metals. The higher malondialdehyde and lower reduced-glutathione levels and the more oxidized glutathione status confirmed the oxidative stress of clams living at the estuary, while no marked increase of antioxidant activities was found this time. Lower metal availability along the second transplant could explain the limited responses in this shorter experiment. Although the status of Guadalquivir estuary has recovered since Aznalcóllar spill, continuous monitoring is needed to confirm its progress and to be alert to possible deterioration after heavy rains. [source] Online collection and analysis of X-ray fluorescence spectra on the macromolecular crystallography beamlines of the ESRFJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 2 2009Gordon A. Leonard X-ray fluorescence (XRF) measurements on solutions or crystals of biological macromolecules provide additional information that can be used in structure determination and/or refinement protocols. Here details are presented of an experimental setup, employed on all the ESRF Macromolecular Crystallography Group beamlines, that allows the online collection and qualitative analysis of XRF spectra. This experimental setup uses a highly attenuated beam and short exposures, meaning it is minimally destructive but retains high sensitivity. [source] Focusing capillary optics for use in solution small-angle X-ray scatteringJOURNAL OF APPLIED CRYSTALLOGRAPHY, Issue 1 2007Jessica S. Lamb Measurements of the global conformation of macromolecules can be carried out using small-angle X-ray scattering (SAXS). Glass focusing capillaries, manufactured at the Cornell High Energy Synchrotron Source (CHESS), have been successfully employed for SAXS measurements on the heme protein cytochrome c. These capillaries provide high X-ray flux into a spot size of tens of micrometres, permitting short exposures of small-volume samples. Such a capability is ideal for use in conjunction with microfluidic mixers, where time resolution may be determined by beam size and sample volumes are kept small to facilitate mixing and conserve material. [source] Solar Radiation-induced Mortality of Marine Pico-phytoplankton in the Oligotrophic Ocean,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2007Susana Agustí ABSTRACT We examined the response of pico-phytoplankton communities sampled at the equatorial, tropical and temperate Central Atlantic Ocean to subsurface underwater solar radiation in order to test the generality of the reported cell mortality for these populations when exposed to high ultra violet radiation (UVR) and photosynthetically active radiation. The natural communities of pico-phytoplankton populations tested experienced high cell mortality when exposed to high solar radiation, despite inhabiting tropical waters. Synechococcus and eukaryotes were more resistant to solar radiation than Prochlorococcus. The decay rates of all pico-phytoplankton groups examined tended to be much higher when exposed to total solar radiation than when UVB-R was filtered out. We also show that even short exposures of 30 min to high solar radiation were able to induce cell mortality in Prochlorococcus. The variability in the decay rates of living Prochlorococcus cells were strongly related to the condition of the original population. However, Synechococcus decay rates were higher in populations from the tropical area, with eukaryotes sensitivity increasing with increasing the trophic degree. The data reported in this study and in the literature revealed contrasting capacities of Prochlorococcus, Synechococcus and eukaryotes to survive under high solar radiation. Although the mechanisms involved are as yet unclear, their elucidation may help explain niche partitioning among these organisms in the ocean. [source] | ||||||||||||||||